Cervical length

Last revised by Dr Mostafa El-Feky on 15 Apr 2020

In obstetric and gynecological imaging, the cervical length is defined as the distance between the internal cervical os and the external cervical os.

Radiographic assessment

Ultrasound
  • the cervical length is most accurately assessed on a transvaginal scan with an empty bladder
  • in a normal gravid situation, the cervical length is considered to be at least 30 mm (3 cm)
  • the presence of a full bladder can increase the cervical length particularly on a trans-abdominal scan

See also

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Cases and figures

  • Case 1: normal second trimester scan
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